Summary Alzheimer?s disease (AD) is now frequently diagnosed in its early stages. In addition to the stressors presented by any chronic disease, an older couple?s ability to keep their relationship intact may be undermined by the specific and progressive symptoms of AD. Until now, most psychosocial research in dementia has focused either on the person with AD or on the caregiver separately. Our study will focus on the relationship between them. We will acquire qualitative data from 32 older couples (64 individuals) about the characteristics of their relationship from the perspective of both members of the couple by conducting focus groups. We will then recruit a culturally and racially diverse sample of older adult couples [300 older adult couples (600 individuals)], the members of which will range from cognitively normal through early dementia at baseline. Follow-ups will occur at 6 month intervals for three years (six assessments) and include both members of the couple through the early stage of Alzheimer?s disease and only the caregivers when participants transition to the middle and late stages. We include cognitively normal couples to serve as a reference group, to enable an understanding of change. Our psychosocial assessment includes measures of cognitive function, activities of daily living and behavior, as well as social support, coping, mental health and self-rated physical health, as well as time to transitions such as residential care placement. The information we obtain will be used to conduct both cross- sectional and longitudinal analyses, develop typologies of relationships, and enable us to investigate the effect of these relationship types on outcomes such as emotional and physical health of both members of the couple, as one member becomes increasingly impaired by Alzheimer?s disease. By following the couples over time, we will be able to track changes in relationship style along with change in cognitive, functional and behavioral status, social support and health outcomes. We will develop tentative typologies and a causal model based on baseline data. The longitudinal study will enable us to corroborate or refine the model and elucidate the relationship styles and changes that are most likely to maintain the well-being of both members of the couple. In our prior experience, the most powerful mediator of outcome is social support, and we plan to see what role that plays in mental and physical health outcomes in this study as well. We expect to find that as dementia advances, the well spouse will have to modify his or her expectations for support from the ill spouse, and that there will be better outcomes if s/he has more satisfactory emotional support from others, particularly family members. The results of this study will include the development of statistical models, and descriptions of couple typologies that will enable us to design interventions to help couples to adapt successfully and minimize the negative effects of Alzheimer?s disease on their relationship and on health outcomes and care cost.